KDX220 Running Rich Issue

gopat · Jun 19, 2007

All,
I just bought a box stock 2000 kdx220 that had set for about 2 years. I replaced the gas, cleaned the carb and it idles great, but it will bog out above 1/4 throttle. The pilot jet was plugged, but there was no varnish or crud in the carb. I could not remove the needle jet orfice where the main jet attaches but it was very clean and spray carb cleaner really flies through it... The float level is good.

Additionally, the compression feels good, the piston and bore are very clean, but I have yet to verify if the power valve is OK. The mains and top end bearings are all in good shape (tight). I removed the air filter and stock silencer and it still runs so rich that it will bog and die after 1 minute of operation with the plug being soaking wet... FWIW, the spark seems strong, as it will jump from the electrode to the plug side wall with a blue spark.

Any ideas what I might have missed? Any ideas what might cause it to run extremely rich?
Thanks!

crhines · Jun 19, 2007

What size main jet and pilot are you running?

gopat · Jun 19, 2007

Stock.... The main is 145 and the pilot I believe is 42 or 45.

adam728 · Jun 19, 2007

Is the choke hanging up?

gopat · Jun 19, 2007

No. This baby idle nicely.... A choke issue would screw idle up... The carb is very clean. Can you think of anything NON-Carb related that could do this? For example, a dirty air filter or a clogged exhaust has been ruled out but could cause a very rich condition...

I am almost tempted to consider the CDI box having a timing issue (not advancing)... I am stumped...

Green Hornet · Jun 19, 2007

How long do you let it idle????

crhines · Jun 19, 2007

I'm not convinced the issue is due to running rich. When my 220 was stock my plug would run black and wet with a 145 main unless I was constantly on the pipe - Still ran ok.

Is motor getting enough fuel from the tank?

gopat · Jun 19, 2007

Problem SOLVED!!!

Ha, It was the plug! Yep, the plug looked brand new (white and sharp edges) and probably was brand new before storage, then a few kicks with some of the residual bad gas and you get a bad plug. What fooled me was that the plug produced enough spark to start and run @ 1/4 throttle, but not much beyond that... Big lesson learned here, don't trust appearances. Thanks for your help and happy bikin...
gopat

crhines · Jun 20, 2007

good to hear. Also, if you have the stock piston you might consider replacing it with a Wiseco. I bought my 99' 220 used and the factory piston self destructed on my 2nd ride (20 miles out in the sand) - not a good experience. Had to split the cases to clean out all the shrapnel.

gopat · Jun 20, 2007

Interesting advice. In my wrenching days (15 years ago), Wiseco was considered second rate to OEM and only used if you were desperate...

What are the minimum and maximum piston to cylinder clearances that you would recommend? Also, what brand oil and ratio and spark plug do you run?

crhines · Jun 20, 2007

I run BR7ES plug - not sure about the piston specs. Lately I've been running Amsoil Interceptor oil - works fine. There are lots of good oils out there as long as they're synthetic. Motul is a great oil.

The 220's are known for having week OEM pistons - do a search. The piston skirt tends to crack off then grind itself into a million pieces. The Wiseco are much stronger. I don't believe the 200 OEM pistons are known to have the same issue (that I'm aware).

adam728 · Jun 20, 2007

Funny you should bring up the "second rate" piston thing. That was a topic of discussion with a big engine builder in Phoenix a few months back. He said Wiseco had a bad name for itself back in the day, but now he would never hesitate to use one. He recommended 0.04-0.05 clearance for the fordged pistons in most engines, and closer to 0.03 for cast. Again, depending on the engine and intended use (for example, a trail ridden CR500 won't need as much clearance as a dune-bound CR250).

The KDX220 pistons are crap, very poor casting with many flaws. I recieved a new one under warrenty and wouldn't put it in, it looked horrible. There appeared to be a lot of porosity, and numerous "cracks" where the material did not completly fill the mold on the skits. All stress risers just asking to take out an engine. I bought a Wiseco instead.

I run a BR8ES plug, never fouled one, even when hardly creeping along trails that are better suited to a trials bike, mountain goat, or Sherpa.

Synthetic oil is almost a must in the KDX, unless you enjoy cleaning the overly complicated power valve setup.

ridejunky · Jun 20, 2007

Since the topic of oil has been brought up I thought I'd put my 2c in.
You will find many brand loyalists and yes, some brands may be better than others in certain areas. Ive tried most and what I've found is that it is more important to mix at the right ratio in small batches(just what you need for the day) than what brand you buy i.e. when its hot ,use more oil to facilitate leaner fuel/air with more lubrication and visa versa

KDX220 Running Rich Issue

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